In spite of difficulties impacting objectivity and reproducibility due to its dependence on the technical and diagnostic ability of each examiner, ultrasonography (US) in general can evaluate very well soft tissue lesions, especially small lesions of 1 cm or less in size. US can reliably delineate the nature of several lesions, and can detect dilated mammary ducts and lymph nodes. On the other hand, US may miss ductal spread or lymph node metastasis of breast cancer, especially if the lesions are too minute to be detected by the instrument. US should be used together with X-ray or MR mammography to prevent false negative cases. US is useful for evaluating the local nature and characteristics of cancerous lesions such as size, invasiveness, histological type, intraductal spread etc, and can evaluate regional lymph node and liver metastasis for pre-treatment staging. In addition, US-guided techniques are essential for preoperative pathological diagnosis by FNAC or CNB and for marking the marginal line for partial mastectomy. US should be more actively used to monitor intra-mammary recurrence after breast conserving surgery.